Non-volatile memory devices are in use today for storing digital pictures, computer files, digitally recorded music and so on. It is common to find non-volatile memory devices in everyday electronics such as computers, digital cameras, MP3 players, answering machines, cell phones, etc.
Non-volatile memory device comes in various forms. One example of a non-volatile memory device is a magnetic disk, as can be found in many computer hard drives. Another example is an optical disk such as a CD-R/W. Yet another example is a solid state memory circuit such as an electrically erasable and programmable read-only memory (EEPROM), a specific example of which is a flash memory device. A flash memory device utilizes high voltages to erase a block of memory cells in one operation, allowing these cells to then be reprogrammed with new data. By virtue of their robustness, convenience and low cost, solid state memory devices, particularly flash memory devices, have gained immense popularity in the marketplace and are expected to become even more dominant as the demand for non-volatile memory continues to grow unabated.
In certain non-volatile memory systems, data and control signals are transferred between the controller and memory devices in parallel using a parallel bus (this configuration is sometimes referred to as “multi-drop”). There are several disadvantages associated with transferring data and control signals between a controller and a memory device utilizing a parallel bus. One disadvantage relates to the complexity involved in implementing such a system. For example, the number of connections needed to implement the parallel bus may be quite significant and require the use of multi-layered printed circuit boards (PCBs). Another disadvantage relates to signal quality in the memory system. For example, parallel buses tend to be susceptible to crosstalk, signal skew, signal attenuation and noise, which may affect the quality of the signals carried by the connections. Yet another disadvantage associated with many parallel bus designs relates to power consumption. Parallel buses tend to require a significant amount of power in order to drive the signals on the bus.
To address shortcomings associated with parallel buses, some memory systems incorporate serial bus designs for transferring data and control signals between the controller and the memory devices. Serial bus designs tend to utilize fewer connections and thus are not as complex and as susceptible to problems associated with parallel bus designs.